Wolves in Yellowstone
The following exert describes the reintroduction program of the grey wolf back into Yellowstone.
Yellowstone National Park, located primarily in northwest Wyoming, is at the heart of the Greater Yellowstone Ecosystem. The rugged terrain and abundance of prey make this temperate ecosystem an ideal environment for wolves. However, due to aggressive eradication efforts in the 1800s and early 1900s, wolves were hunted to the point that they were no longer present in the park. By 1926, the last wolf pack in Yellowstone had been eliminated. The effect of such a change on an ecosystem was not well understood by scientists at that time.
In 1995, a program began to reintroduce wolves into Yellowstone National Park.
During the first several years in which the wolf population was restored, observational studies reported that the diversity of plant species increased, certain songbirds returned, and aquatic ecosystems within the park changed.
1. Elk enjoy eating the leaves of Cottonwood trees. Which of the following represents a food chain with proper arrows showing energy flow that is found in the ecosystem described above. (1 point)
• Cottonwood » Elk « Wolf
• Wolf » Cottonwood » Elk
• Cottonwood » Elk » Wolf
• Elk » Cottonwood « Wolf
Elk » Cottonwood « Wolf
2. Use the graph below to answer the question.
Population Changes in Three Species
Relative Populations
MAA
-wolves
15
20
Time (Years)
25
elk
-cottonwood trees
30
How did the reintroduction of the grey wolf, a carnivore predator, affect the population of the cottonwood trees, a type of producer?
(1 point)
• The cottonwood tree population increased and then stabilized.
• The cottonwood tree population decreased and then stabilized.
• The cottonwood tree population did not change.
• The cottonwood tree population increased and then decreased back to zero.
Based on the graph, the correct answer is: The cottonwood tree population increased and then stabilized.
3. Use the drop down menus to complete the paragraph describing the events related to the reintroduction of the grey wolves into Yellowstone National Park. (6 points)
Before people understood their importance in the ecosystem, the
was hunted almost to
extinction. Because of this, the
population grew much too large. They overgrazed and caused
significant reduction in the population of
When the grey wolf was reintroduced, they began to
naturally
the population of elk. This allowed the cottonwood tree population to
After several years of adjustment, all three populations
and showed healthy oscillation
in the ecosystem.
Before people understood their importance in the ecosystem, the grey wolf was hunted almost to extinction. Because of this, the elk population grew much too large. They overgrazed and caused a significant reduction in the population of cottonwood trees. When the grey wolf was reintroduced, they began to naturally control the population of elk. This allowed the cottonwood tree population to increase. After several years of adjustment, all three populations stabilized and showed healthy oscillation in the ecosystem.
4. What explanation could be generated from the graphs below that show the results of an experiment with two Paramecium species?
In separate containers
In one container
Relative population density
P. aurelia
P. caudatum
P. aurelia
P. caudatum
0
2 4 6 8 10 12 14 16
Days
0
2
4 6 8 10 12 14 16
Days
(1 point)
There is a commensalism relationship between the two Paramecium species and when they are in the same container, one benefits and the other is neither harmed or benefited from this relationship.
There is competition between the two Paramecium species and when they are in the same container, one significantly out competes the other because of this relationship.
There is a mutualism relationship between the two Paramecium species and when they are in the same container, they both benefit from this relationship.
Based on the description, the correct explanation could be: There is competition between the two Paramecium species and when they are in the same container, one significantly outcompetes the other because of this relationship.
8. Using the data from the graph below, what suggestions (select all that apply) can you make about the relationship between the average number of individual geckos found compared to the invasion of the yellow crazy ants? Invaded means that the yellow crazy ants have entered into the environment and non-invaded means that the yellow crazy ants have not entered into the environment. The black bar shows gecko population when the ants have entered into the environment, and the grey bar shows gecko population when the ants have not entered into the environment.
Figure 4:
Gecko numbers
Gecko numbers were counted on
60 random trees in both invaded and non-invaded areas.
Average Gecko Numbers in Vallée de Mai Park
Average number of individuals found
15
10
Yellow crazy ants
=
Invaded
• Non-invaded
0
Seychelles day gecko
Seychelles giant day gecko
Dwarf bronze gecko
Seychelles bronze gecko
Giant bronze gecko
(1 point)
- The invasion of the yellow crazy ants had the most positive affect on the Seychelles day gecko population suggesting that the ants served as an additional food source for the gecko.
The Seychelles glant day gecko, the dwarf bronze gecko, and the Seychelles bronze gecko are more successful in areas where the yellow crazy ants have not invaded.
- The invasion of the yellow crazy ants had the least on the dwarf bronze gecko population suggesting
possible competition between the two species.
• The invasion of the yellow crazy ants had the no affect on any gecko population.
Based on the data from the graph, the suggestions that can be made are:
- The Seychelles giant day gecko, the dwarf bronze gecko, and the Seychelles bronze gecko are more successful in areas where the yellow crazy ants have not invaded.
- The invasion of the yellow crazy ants had the least effect on the dwarf bronze gecko population, suggesting possible competition between the two species.
10. Which system would be best suited for the movement large quantities of adult Salmon? (1 point)
• Upstream System
• Downstream System
• Salmon Canon